u/Flat_Till_9485

This is my first time DMing, and I'm not really a computer guy, so everything is confusing to me. I'm using Roll20 as my tabletop because it's what I'm the most familiar with as a player, and I downloaded a few free asset packs from 2-Minute Tabletop. Now, how do I access them? I see them in my files, but I can't open them or drop them into Roll20.

Also, is there a place where I can keep all the assets in one spot so I can just drag and drop them when needed?

I want something manual, so I can make it exactly how I like. But everything I've found is either premade assets or a generator. I've made a map using the rice method, and I enjoyed it, but it was a pain getting it into the digital realm. If there's something that's similar but online id love to know.